\begin{tikzpicture} % 示意图
    \pgfmathsetmacro{\R}{2.5}
    \pgfmathsetmacro{\r}{2.1}

    \tkzDefPoints{0/0/O}
    \tkzDefPoint(130:\R){A}
    \tkzDefPoint(130:\r){a}
    \tkzDefPoint(50:\R){B}
    \tkzDefPoint(50:\r){b}
    \tkzDefPoint(90:\R){C}
    \tkzDefPoint(90:\r){c}

    \tkzFillSector[pattern={mylines[angle=45, distance={3pt}]}](O,B)(A)
    \tkzFillSector[fill=white](O,b)(a)
    \tkzDrawArc[thick](O,B)(A)
    \tkzDrawArc[thick](O,b)(a)
    \tkzDrawSegments[thick](A,a B,b)
    \tkzDrawSegments[dashed](O,a  O,b  O,C)

    %
    \tkzDrawSegments[dim={$l$,-1em,pos=.6}](a,b)

    \tkzInterLL(a,b)(O,c)  \tkzGetPoint{x}
    \tkzDefPointOnLine[pos=1.5](x,b)  \tkzGetPoint{y1}
    \tkzDefPointBy[translation=from x to y1](c)  \tkzGetPoint{y2}
    \tkzDefPointBy[translation=from x to y1](C)  \tkzGetPoint{y3}
    \tkzDefShiftPoint[y1](0,-.3){y1'}
    \tkzDefShiftPoint[y3](0, .3){y3'}
    \tkzDrawLines[add=0 and 0.1](x,y1  c,y2  C,y3)
    \tkzDrawSegments[-Latex](y1',y1  y3',y3)
    \tkzLabelSegments[centered,rotate=90](y1,y2){$h$}
    \tkzLabelSegments[centered,rotate=90](y2,y3){$k$}
\end{tikzpicture}

